Thermally responsive locking means for oven door latching mechanism

ABSTRACT

A sliding latch mechanism for the door of the heated cavity such as an oven door. The latch mechanism includes a latch handle and a pivoted latching bolt for swinging out and engaging the door. There is a thermally responsive locking means for locking the door latching mechanism in its closed position. The locking means comprises a single point snap-acting thermostat and a movable pawl whereby at a sensed temperature of about 600*F. the thermostat will cause the shifting of the pawl for cooperation with the latch mechanism. The thermostat includes switch means for both the power and control circuits for the heating means of the oven.

United States Patent 1191 1111 3,815,942 White 1451 June 11, 1974 1 TI-IERMALLY RESPONSIVE LOCKING 3,350,542 10/1967 Getman 219/412 MEANS FOR OVEN DOOR LATCHING 3,390,909 7/1967 Nagel 292/201 3,656,182 4/1972 Staples 337/319 MECHANISM James A. White, Louisville, Ky.

General Electric Company, Louisville, Ky.

July 31, 1972 Inventor:

Assignee:

F iled:

Appl. No.:

US. Cl 292/113, 292/201, 292/DIG. 66, 292/DIG. 69

Int. Cl. E05c 5/00 Field of Search 219/398, 412; 292/113, 292/203, DIG. 66, DIG. 69, 201; 337/319 References Cited UNITED STATES PATENTS Primary Examiner-Richard E. Moore Attorney, Agent, or Firm-Richard L. Caslin [57] ABSTRACT A sliding latch mechanism for the door of the heated cavity such as an oven door. The latch mechanism includes a latch handle and a pivoted latching bolt for swinging out and engaging the door. There is a thermally responsive locking means for locking the door latching mechanism in its closed position. The locking means comprises a single point snap-acting thermostat and a movable pawl whereby at a sensed temperature of about 600F. the thermostat will cause the shifting of the pawl for cooperation with the latch mechanism. The thermostat includes switch means for both the power and control circuits for the heating means of the oven.

3 Claims, 6 Drawing Figures 8O 9O I s @LA,

nzn E:

THERMALLY RESPONSIVE LOCKING MEANS FOR OVEN DOOR LATCHING MECHANISM BACKGROUND OF THE INVENTION The present invention relates to a latching means for the door of a baking oven, and particularly to a safety locking means to insure that the door may not be unlatched when the oven is operating in a high temperature range above normal cooking temperatures.

This invention is another outgrowth of the development of a pyrolitic self-cleaning oven as is taught in the patent of Bohdan Hurko U.S. Pat. No. 3,l2l,158 which is assigned to the General Electric Company, the assignee of the present invention. Such a self-cleaning oven, whether it be electric or gas, performs the normal cooking functions of baking and broiling in a temperature range between about l50 and 550F., as well as a high temperature automatic oven cleaning operation during which the temperature is raised to a maximum somewhere between 750F. and about 950F. for removing all of the food soil and grease spatterthat accumulates on the walls of the oven liner and inner surface of the oven door during normal cooking. Such a cleaning method may be characterized by the term pyrolysis which meansthe chemical decomposition of matter by the application of heat. The oven soil is converted into harmless gaseous degradation products which are returned to the atmosphere.

The present invention is concerned with means for insuring that the oven door is both closed and locked before the self-cleaning oven cycle can be initiated, as well as to insure that the oven door cannot be unlocked prematurely as long as the oven temperature is above the maximum normal cooking temperature of about 600F.

SUMMARY OF THE INVENTION A door latching mechanism comprising a mounting bracket with both a latching bolt and a handle lever pivotally mounted on the bracket and joined together through a lost motion connection so that movement of the handle lever causes a movement of the latching bolt into either an open position free of the door or a closed position engaging and locking the door in its closed position. A thermally responsive locking means is furnished for locking the door latching mechanism in its closed position. This locking means comprises a single point thermostat and a movable pawl. The thermostat has a snap-acting responder that is furnished with a remote temperature sensing probe as well as an actuator means interposed between the responder and the pawl whereby at a sensed temperature of about 600F. the responder will function to shift the position of the pawl.

The principle object of the present invention is to provide a door latching mechanism of a high temperature heated cavity with a thermally responsive means for operating a movable locking pawl at a critical tem- A further object of the present invention is to provide a high temperature oven door latching mechanism wherein the latching mechanism cannot be operated at temperatures above about 600F. by virtue of the cooperation of a hydraulic thermostat that is provided with a snap-acting motion to move a locking pawl into cooperation with the latching mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS My invention will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 is a left side elevational view of a free-standing electric range having an oven door latching mechanism embodying the present invention.

FIG. 2 is a fragmentary plan view on an enlarged scale taken on the line 22 of FIG. 1 to show the door latching mechanism cooperating with the locking pawl and snap-acting thermostat assembly of the present invention, wherein the latching mechanism is set in its open or unlocked position.

FIG. 3 is a side elevational view of the door latching mechanism and thermostat and pawl locking means of the present invention taken on the line 3-3 of FIG. 2.

FIG. 4 is a side elevational view similar to that of FIG. 3 except the door latching mechanism has been moved into its locked position and the oven temperature is above the critical temperature of about 600F. as the locking pawl has been allowed to drop into locking engagement with the latching mechanism due to the operation of the hydraulic thermostat.

FIG. 5 is a cross-sectional elevational view on an enlarged scale of the hydraulic thermostat to show the inner workings.

FIG. 6 is a schematic diagram of both the power and control circuits of the high temperature self-cleaning oven that is furnished with an oven door latching mechanism and locking arrangement of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to a consideration of the drawings and in particular to FIG. 1, there is shown for illustrative purposes a free-standing electric range 10 having a top cooking surface 11 with a plurality of surface heating elements 1.2, an oven cooking cavity 13 beneath the top cooking surface, a front-opening oven door 14 hinged along its bottom edge 15, and a backsplash 16 arranged along the back edge of the cooking surface 11 and including in its front face a control panel with all the manual and visual control components 17 mounted therein for governing the energization of the various heating means of the range. The oven cooking cavity 13 includes two standard electric heating elements; namely, a lower bake element 20 arranged along the bottom wall of the box-like oven liner 22, and an upper broil unit 24 which is located adjacent to the top wall of the oven liner. A third heating element or mullion heater is useful in self-cleaning ovens to extend around the front portion of the oven liner 22 adjacent the door opening to furnish supplementary heat in this area to obtain generally uniform oven wall temperatures. As in conventional ovens, there is a thick layer 25 of thermal insulation such as fiberglass surrounding the walls of the oven liner 22 for retaining the heat generated within the cooking cavity 13. Moreover, the oven door 14 is an insulated door construction so as not to allow excessively high temperatures to exist on the outer surface of the door which might otherwise constitute a safety hazard.

The oven door is provided with a substantially continuous woven fiberglass door gasket 26 which is adapted to engage the front flange of the oven liner and substantially seal the door gap between the oven liner and the door when the door is latched during the high temperature self-cleaning operation. This gasket 26 is provided with a small opening (not shown) between its two spaced butt ends to allow a predetermined amount of air to pass into the oven cavity during the selfcleaning cycle for sweeping the gaseous degradation products from the cavity and through a smoke eliminator (not shown) adjacent the oven exhaust vent before returning these gases to the kitchen atmosphere. For a more detailed explanation of a satisfactory door gasketing arrangement attention is directed to the patent of Clarence Getman U.S. Pat. No. 3,189,020, which is also assigned to the same assignee as is the present invention.

The door latching mechanism of the present invention is identified by the numeral 30 in FIG. 1 and it is preferably located within the oven cabinet or range body above the door opening and above the top layer of thermal insulation 25. An oven door latching mechanism is standard equipment on a self-cleaning oven where the oven air temperature is raised to a maximum somewhere between 750F. and about 950F. for the reason of controlling the amount of air that enters the oven cooking cavity so as to control the rate of cleaning the soil and avoiding ignition. This is not just a preference, this is a necessity. Referring particularly to the detailed view of FIGS. 2-4, the latching mechanism 30 is shown as comprising a mounting bracket or base plate 32 which is generally of flat sheet metal construction with an upturned front flange 33 which is adapted to be fastened against the inner surface of the front door frame 35 of the oven body.

The particular door latching mechanism 30 that is illustrated is generally the same as is described in the patent of Joseph S. Fox, Sr., US. Pat. No. 3,367,697, which is also assigned to the same assignee as is the present invention. This latching mechanism will be described briefly in order to facilitate the understanding of the background or environment in which the present invention is placed. The two main elements of the door latching mechanism 30 is a latch handle 37 and a pivoted latching bolt 39 which has a front hook portion 40 which is adapted to swing out from within the oven body through a horizontal slot 42 in the upturned flange 33 and the front door frame 35 and engage within a mating slot 44 or keeper as shown in FIG. 4 on the inner surface of the oven door 14 for gripping one vertical side of the mating slot for maintaining a fixed relationship between the door and the oven frame. The latching bolt 39 is a little difficult to identify because it is partially covered by a door sensing bar 46 that generally overlies the latching bolt 39 and functions to prevent the full movement of the latching mechanism to its closed position unless the oven door 14 is first in its closed position as seen in FIG. 4. If the oven door is not in its closed position when the latch handle 37 is moved from the open position of FIG. 2 to the closed position of FIG. 4 then the hook portion 45 of the door sensing bar 46 will engage the edge 47 of the slot 42 and jam in an intermediate position so that no further movement of the latch mechanism towards a fully closed position is possible. However, if the oven door 14 were closed then the edge of the keeper slot 44 of the door would cause the door sensing bar 46 to swing back in a counter clockwise direction and free the latching bolt to engage the door. The latch handle 37 is an elongated bar that is pivoted to the base plate 32 by a fixed pivot pin 48. The front portion of the latch handle 37 is offset upwardly so as to be spaced and not interfere with the swinging action of the latching bolt 39, as is best seen in FIG. 4. The handle extends outwardly from the oven body through an elongated slot 50 so as to be accessible from the front of the oven and yet not interfere with the movement of the oven door 14.

There is a lost motion connection between the latching bolt 39 and the base plate 32 by means of a fixed pin 58 fastened in the base plate and extending upwardly into an elongated longitudinal slot 60 in the latching bolt. The innermost end of the latching bolt 39 is furnished with a through-pin 52 with its lower end captured in a cam slot 56 and its upper end serving both as the pivot means for the door sensing bar 46 and confined within a cam slot 54 formed in the latch handle 37.

The door sensing bar 46 is provided with a bent-up tab 62 along its left side near the center thereof, and the latching bolt 39 is provided with an opposing spaced tab 64. A compression or torsion spring 66 is sandwiched between the two tabs 62 and 64 to normally bias the sensing bar in a clockwise direction about its pivot pin 52 so it overlies the hook portion 40 of the latching bolt 39.

An over-center spring 70 is connected at one end to a vertical flange 72 of the base plate 32 and at its other end near the pivoted end of the latch handle 37 as at 74 so that the latch handle is unstable and must assume either one of two positions; namely, a fully open position of FIG. 2 or a fully closed position of FIG. 4.

What has been described above in detail is more or less a standard oven door latching mechanism 30. The thermally responsive locking means of the present invention is identified by the numeral 80, and it comprises two main elements; namely, a single point, snapacting thermostat 82 and an overlying pivoted pawl 84 which is activated by the thermostat. First, an extension plate 86 is attached to the back end of the base plate 32 and the thermostat 82 is supported from this extension plate 86 by means of a mounting flange 88. At the rear of this extension plate 86 is a vertical flange 90 which rises above the thermostat 82. One side of the top edge of the flange 90 is folded forwardly to form a tab 92 having a hole for receiving a rivet 93 that also extends through one end of the pawl 84 and serves as the pivotal means for the pawl.

The rear end of the base plate 32 is folded upwardly as at 95, and then at its top it is folded forwardly as at 97. Both flanges-95 and 97 are slotted at 99 to receive the front end 98 of the locking pawl 84 therein. The purpose of supporting and of guiding the front end 98 of the pawl 84 in the slot 99 is to reinforce the pawl since the pawl has a downwardly projecting finger 100 that is adapted to slip into a notch 102 in the latch handle 37 adjacent the pivot pin 48 when the latch handle is in its closed position as is seen in FIG. 4.

The thermostat 82 includes a temperature responder having a snap-acting spring mechanism 105 as is seen in the detail view of FIG. 5. This spring mechanism is in the form of a combined blade and amplitude spring that is generally of elongated rectangular configuration. The blade is mounted in semi-cantilever fashion and is acted upon by a hydraulic diaphragm assembly 107 that is complete with a thin capillary tube 108, which may be several feet in length, and is provided on its free end with an elongated temperature sensing bulb or probe 110, which is illustrated in FIG. 1 as being mounted within the oven cavity 13 adjacent the back wall of the oven liner 22 and near the top portion thereof. This type of single point hydraulic thermostat 82 is generally of the type that is disclosed in the recent patent of Paul Staples US. Pat. No. 3,656,182, which is also assigned to the assignee of the present invention. This thermostat responder has a hollow housing 112 formed of insulating material that is divided in half by a transverse partition 114 into an expansion chamber 116 at the right that houses the diaphragm assembly 107 and into a switch compartment 118 at the left in which a switch mechanism 120 is housed. The transverse partition 114 is left open at the top, as at 122, and this opening accommodates the elongated snap-acting spring mechanism 105 which overlies the diaphragm assembly 107. A horizontal partition 124 extending sidewardly from the top of the partition 114 subdivides the left side of the housing 112 into a lower switch compartment 118 and an upper spring compartment 126 which is accessible to the expansion chamber 116 through the opening 122 in the transverse partition 114. Thus, it can be seen that the spring mechanism 105 extends from the expansion chamber 116 into the upper spring compartment 126 for connection with the switch mechanism 120 in the switch compartment 1 18.

This switch mechanism 120 is in the form of a single pole double throw switch mechanism that is fully disclosed in the beforementioned Staples US. Pat. No. 3,656,182, and it is not fully described and illustrated here for the sake of brevity. A vertical plunger 128 of insulating material is carried by the spring mechanism 105 and joined to the switch mechanism 120 to serve as an actuator means for the switch mechanism. The spring mechanism 105 extends through and is connected in a suitable opening in the plunger 128 and serves to move the plunger in either an up or down direction as its spring mechanism snaps up or down depending upon whether it is an expansion or contraction of the diaphragm assembly 107 at a critical sensed temperature within the oven cavity of about 600F.

The thermostat housing 112 is supplied with two removable cover means; namely, a folded sheet metal cover 130 at the left of generally U-shape and a simple metal cover plate 132 at the bottom of the right side for closing the expansion chamber 116. The folded sheet metal cover 130 closes the top wall of the housing thereby closing the spring compartment 126, and then this cover extends down the left side of the housing as at 134 and finally extends beneath the housing at 136 to close the switch compartment 118. An adjustment screw 138 that is threaded through the top of the housing engages the supported end of the cantilever spring mechanism 105 and serves as a calibration screw. A second adjustment screw 140 is threaded through the bottom cover plate 132 and engages a mounting bracket 141 for the diaphragm assembly 107 for serving as a second calibration means. The cover plate 132 has a mounting flange 88 at one end that serves to support the thermostat on the extension base plate 86, as is best illustrated in FIG. 3 of the drawing.

The vertical plunger 128 is an elongated member that extends up through a suitable opening 142 in the top of the cover plate 130, and it is adapted to bear against the underside of the movable pawl 84, as is best seen in FIG. 3. The pawl 84 is provided with a vertically adjustable plate 144 which is adapted to serve as the bearing plate for the top of the plunger 128 and to allow for some adjustment of the position of the pawl to take care of manufacturing tolerances. This plate 144 is pivoted at one end to the pawl by means of a rivet fastener 146 in a cantilever fashion, and the free end of the plate 144 is locked by a screw and nut assembly 148 which may be loosened for adjustment and tightened for locking the plate 144 in place.

The switch mechanism of the single point, snapacting thermostat 82 0f the present invention is designed to be used as one of the control components of a self-cleaning oven whose power and control circuits are illustrated in the schematic diagram of FIG. 6. The oven is furnished with an electrical service of threewire source of power; nominall y of 236 V, single phase, 60 Hz, A.C., which is usually available in the average residence having adequate wiring. This voltage source is connected to the oven through a three-wire cable having a pair of line wires L and L with voltage of 236 V therebetween, and a grounded Neutral conductor N with half voltage or 118 V measured across any line wire L or L with a Neutral conductor N for supplying the electrical load of the oven. This electrical load of the oven is characterized by three heating elements; a baking element 20, a broiling element 24, a smoke eliminator 182 in the oven vent and an auxillary heater or mullion heater which is adapted to be positioned around the oven liner 22 adjacent the front thereof so as to supply supplementary heat in the vicinity of the oven door 14 so as to obtain generally uniform temperature conditions within the oven during the selfcleaning oven cycle. These main heating elements 20, 24 and 160 are arranged in various circuits by virtue of an oven selector switch 162 that is capable of setting up different combinations of heating elements at different voltages to obtain a variety of heating rates. A manually settable, solid state, oven thermostat 164 is also furnished for controlling the temperature within the oven at preselected temperatures during baking operations, and at separate maximum temperatures during broiling, as well as during the automatic oven cleaning operation. This oven thermostat 164 is in series with a hotwire relay 166 that is in turn in series with the heating elements 20, 24, 160 and 182 for opening and closing the power circuit to the heating elements as a function of the oven actual air temperature with relation to the temperature predetermined or preset by the thermostat 164.

The oven selector switch 162 is provided with a series of four line terminals L, N, L and L as well as a series of three load terminals K, J, and P. This selector switch 162 is also provided with a plurality of switch contacts 171-179. These switch contacts are labeled with the particular cooking or cleaning operation that is involved when such contacts are closed. For example, during a Baking" or a Time-Baking" operation,

contacts 171, 172, 177 and 178 are closed. During a Broiling operation, contacts 175 and 176 are closed. During a Cleaning Cycle, contacts 172, 173, 174, 175, 178 and 179 are closed.

The Baking circuit has the bake element 20 operating at full wattage across lines L, and L at 236 V through the thermostat responder 82 which connects the selector switch 162with line L, while the other end of the bake element 20 is connected to the hot-wire relay 166 and through the smoke eliminator 182 to the other line L The responder 82 has two sets of switches previously described as switch mechanism 120. This mechanism is a single pole double throw mechanism comprising a first switch 186 and a second switch 188. This first switch 186 is normally closed at oven temperatures below about 600F. for normal cooking operations, while the second switch 188 is normally open at such relative low temperatures and it is closed only when the oven temperature rises above normal cooking temperatures or above about 600F. During the Baking cycle the other two heating elements 24 and 160 are also energized. They are in a series circuit connected back through the thermostat switch 186 to line L, and also connected through the hot-wire relay 166 and smoke eliminator 182 to the line L In the Broiling circuit, only the top broil element 24 is energized, and it is connected across lines L, and L through the thermostat switch 186 as well as through the hot-wire relay 166 and smoke eliminator 182.

If a control component failure should occur during a cooking operation of either baking, time-baking, or boiling, and the oven temperature were to rise above the preset temperature of the oven thermostat 164 and reach an oven temperature above 600F., then the thermostat switch 186 would also be opened by the snapacting spring mechanism 105 of the thermostat responder 82 to open the power circuit to the heating elements and preventing a run away temperature condition. Thus, the responder 82 serves as an overtemperature limit control when the oven is in any normal cooking operation.

During a self-cleaning mode of operation, the oven selector switch 162 is not connected through the responder 82 to line L,, but instead is connected to Neutral conductor N by means of lead 190. However, the second thermostat switch 188 of the responder 82 is connected to line L, and is in series with an oven cabinet cooling fan 192 and a lock indicator lamp 194 which then is connected by lead-196 to a latch switch 198 that funishes power to the primary of a transformer 200 which has a secondary 202 for furnishing low voltage power to the oven thermostat 164 during the cleaning operation. This latch switch 198 is mounted to the base plate 32 of the door latch mechanism 30 as is best seen in FIG. 2 such that the oven door 14 must be closed and then latched before it is possible to initiate the self-cleaning oven cycle. This latch switch 198 also has a normally closed set of contacts 222 when the door latching mechanism 30 is unlatched for energizing the transformer for use during normal cooking operations.

The oven selector switch 162 has another switch 203 with contacts 204, 205 which are normally open during cooking operations, and are adapted to be closed when the selector switch is set into its Clean position for connecting the fan 192 and lock lamp 194 from lead L, by

means of leads 207 and 208 to Neutral conductor N. The oven selector switch 162 also includes a single pole double throw switch 210 having a first switch 212 and a second switch 213. The switch 213 is connected in series with an oven timer 215 to provide a timed cycle for both baking and Cleaning in a circuit from Neutral conductor N and through an oven cycling lamp 217 that is connected to line L by means of lead 219 through the hot-wire relay 166. This oven selector switch contacts 210 is also connected to the primary of the transformer 200. The latch switch 198 has a set of normally closed contacts 222 which are closed during normal cooking operations for completing a circuit from line L, and thermostat switch 186 by lead 224 through the switch contacts 212 of the oven selector switch 210, then by lead 226 through the primary of the transformer 200 and then through the latch switch contact 222, and back by lead 228 and lead 208 to the Neutral conductor. An oven clean lamp 230 is adapted to be in series with the latch switch contacts 232 and the switch 213 of the selector switch contacts 210 so that whenever the oven clean circuit is completed the oven clean lamp 230 will be energized to indicate to the user that the oven is in readiness for cleaning.

During the self-cleaning operation, the three heating elements 20, 24 and are connected in parallel at half voltage across lines L and Neutral conductor N in order to obtain a heating rate somewhat lower than the heating rate during normal baking operations.

Modifications of this invention will occur to those skilled in this art, therefore it is to be understood that this invention is not limited to the particular embodiments disclosed but that it is intended to cover all modifications which are within the true spirit and scope of this invention as claimed.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A door latching mechanism comprising a mounting bracket with a pivoted latching bolt mounted on the bracket and a handle lever pivotally mounted on the bracket and joined to the latching bolt so that movement of the handle lever causes a movement of the latching bolt into an open position free of the door or a closed position engaging the door in its closed position, thermally responsive locking means for locking the door latching mechanism in its closed position, said locking means comprising a thermostat and a movable pawl, the thermostat being a single point snap-acting thermostat having a responder and a remote temperature sensing probe, and an actuator means interposed between the responder and the pawl whereby at a sensed oven temperature at about 600F. the responder will be actuated to shift the position of the pawl.

2. A door latching mechanism as recited in claim 1 wherein the movable pawl is a pivoted member arranged over the thermostat responder, and the actuator means is a strut member supported by the responder and serving to raise and lower the pawl for a locking engagement with the door latching mechanism.

3. A door latching mechanism as recited in claim 2 wherein the thermostat responder includes interlock switch contact means for controlling a heating circuit into a high temperature range as a function of the door latching mechanism being closed and locked by the said locking means. 

1. A door latching mechanism comprising a mounting bracket with a pivoted latching bolt mounted on the bracket and a handle lever pivotally mounted on the bracket and joined to the latching bolt so that movement of the handle lever causes a movement of the latching bolt into an open position free of the door or a closed position engaging the door in its closed position, thermally responsive locking means for locking the door latching mechanism in its closed position, said locking means Comprising a thermostat and a movable pawl, the thermostat being a single point snap-acting thermostat having a responder and a remote temperature sensing probe, and an actuator means interposed between the responder and the pawl whereby at a sensed oven temperature at about 600*F. the responder will be actuated to shift the position of the pawl.
 2. A door latching mechanism as recited in claim 1 wherein the movable pawl is a pivoted member arranged over the thermostat responder, and the actuator means is a strut member supported by the responder and serving to raise and lower the pawl for a locking engagement with the door latching mechanism.
 3. A door latching mechanism as recited in claim 2 wherein the thermostat responder includes interlock switch contact means for controlling a heating circuit into a high temperature range as a function of the door latching mechanism being closed and locked by the said locking means. 